// Copyright (C) 2014 by Alexandru Cojocaru

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.


fn todigs(n: u32) -> Vec<u8> {
    let mut m = n;
    let mut ds = vec![];
    while m != 0 {
	ds.push ((m%10) as u8);
	m /= 10;
    }
    ds
}

fn fromdigs(v: &Vec<u8>) -> u32 {
    let mut n = 0;
    for d in v.iter () {
	n *= 10;
	n += *d as u32;
    }
    n
}		

fn kaprekar(n: u32) -> u32 {
    let mut ds = todigs(n);
    ds.sort_by (|a,b| a.cmp(b).reverse());
    let n1 = fromdigs(&ds);
    ds.reverse ();
    let n2 = fromdigs(&ds);
    n1 - n2
}

fn brent<F>(f: F, x0: u32) -> (u32,u32)
    where F: Fn(u32) -> u32
{
	let mut pow = 1;
	let mut lam = 1;
	let mut tort = x0;
	let mut hare = f(x0);

	while tort != hare {
	    if pow == lam {
		tort = hare;
		pow *= 2;
		lam = 0;
	    }
	    hare = f(hare);
	    lam += 1;
	}

	let mut mu = 0;
	tort = x0;
	hare = x0;
	for _ in 0..lam {
	    hare = f(hare);
	}

	while tort != hare {
	    tort = f(tort);
	    hare = f(hare);
	    mu += 1;
	}

	(mu,lam)
}

fn main() {
    let b = brent(kaprekar, 61974);
    println!("{}, {}", b.0, b.1);
}